I changed the the source side resistors to 5 ohms, and the V+ input drain resistor from 2.2K to 1K. Thats giving me about 10V across the Jfets. No more crazy distortion.

It's making music now. It sounds well...good I think.

Also, The voltage across D-S of the Jfet is 10.1V on one channel and 9.5V on the other. Does this indicae a bad match on the jfets?

It's got lots of noise If I crank up the volume without a signal. Maybe I need to sort out the wiring a bit. But it's working.

What voltage should I be aiming for across the Jfets? They are BL grade. I am starting to understand the relationship between the drain and source resistor to the distortion and voltage across the Jfets.

Also, I have a Pass f5 that I jacked up the gain by using 200ohm gain resistors instead of the stock 100 ohm. So, I have more feedback and 6db more gain than stock in the amp. maybe I should go back to the 100ohm.

What is the smallest value cap I could use on the output? I have some Ampohm 2.2uf's would they be useable?

I have seen some people suggest a 5.6ish UF cap, i am using an 8.2UF and have no DC on output.

I finally got mine sounding good by playing with the source and drain resistor values. I'd pick up an assortment of resistor values to play with for the source and drain if you don't have a lot on hand already.

Also, I had a lot of hum and noise when turned up. It was my unshielded interconnects. Never noticed it when using a passive preamp setup.

Hi all, thanks for an interesting thread. I have started dabbling with solid state audio recently starting with a DCB1 and the ACA, both originating from Mr Pass (Thanks Nelson). Compared to my valve power amp (a 6L6 SE with EF86 drivers) I have to crank up the LS volume on my DCB1 to get sufficient SPL from my 90dB speakers.

Now I'm planning to build a jBOZ preamp and B1 buffer in the same case. As the two designs have have a potentiometer at their inputs I would like ask where is the best place to have the volume control: at the jBOZ input or at the B1? I am thinking of putting a 25K trimmer at the input of the other design.

Is this plan OK, and will it work? I don't want to have two volume controls on the front facia, one to control the JBOZ and another for the B1.